1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a method of manufacturing the same.
2. Discussion of the Related Art
Until recently, display devices have typically used cathode-ray tubes (CRTs). Presently, many efforts and studies are being made to develop various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs), as a substitute for CRTs. Of these flat panel displays, LCD devices have many advantages, such as a higher resolution, a lighter weight, a thinner profile, a more compact size, and low voltage power supply requirements.
In general, an LCD device includes two substrates that are spaced apart and face each other with a liquid crystal material interposed between the two substrates. The two substrates include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the liquid crystal material. An alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field into the direction of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field.
FIG. 1 is a perspective view illustrating an LCD device according to the related art.
Referring to FIG. 1, the LCD device 1 includes an array substrate 10, a color filter substrate 20 and a liquid crystal layer 30. The array substrate 10 includes a gate line 14 and a data line 16 on a first substrate 12 that cross each other to define a pixel region P. A pixel electrode 18 and a thin film transistor Tr, which acts as a switching element, are positioned in each of the pixel region P. The thin film transistors Tr, which are disposed adjacent to a position where the gate lines 14 and the data lines 16 cross, are disposed in a matrix form on the first substrate 12. The color filter substrate 20 includes a color filter layer 26 including red (R), green (G) and blue (B) color filter patterns 26a, 26b and 26c in respective pixel regions P on a second substrate 22, a black matrix 25 between the color filter patterns 26a to 26c, and a common electrode 28 on the color filter layer 26 and the black matrix 25.
Spacers are located between the array substrate 10 and the color filter substrate 20 to maintain a cell gap therebetween. The spacers may be a ball spacer or a patterned spacer. Further, a seal pattern is formed along peripheral portions of the array substrate 10 and the color filter substrate 20 to attach the array substrate 10 and the color filter substrate 20 and prevents liquid crystal molecules of the liquid crystal layer 30 from leaking. Further, a polarizing film may be formed on at least one of the outer surfaces of the array substrate 10 and the color filter substrate 20. Further, a backlight supplying light is located below the array substrate 10.
FIG. 2 is a plan view illustrating an LCD device including a patterned spacer according to the related art, and FIG. 3 is a cross-sectional view taken along a line of FIG. 2.
Referring to FIG. 2, the LCD device 35 includes a gate line 43 and a data line 55 crossing each other on a first substrate 40 of an array substrate to define a pixel region P. Red (R), green (G) and blue (B) color filter patterns 76a, 76b and 76c are formed in red (R), green (G) and blue (B) pixel regions P, respectively, of a color filter substrate. In each pixel region P, a gate electrode 45 connected to the gate line 43, a source electrode 58 connected to the data line 55, and a drain electrode 60 spaced apart from the source electrode 58 are formed.
The drain electrode 60 is connected to a pixel electrode 67 through a drain contact hole 65. The gate electrode 45, and the source and drain electrodes 58 and 60 form a thin film transistor Tr.
Patterned spacers 83 are formed between the first substrate 40 and a second substrate 70 and spaced part from one another.
Referring to FIG. 3, the gate electrode 45 and the gate line 43 are formed on the first substrate 40, and a gate insulating layer 47 is formed on the gate line 43. A semiconductor layer 50 is formed on the gate insulating layer 47 over the gate electrode 45. The semiconductor layer 50 includes an active layer 50a and an ohmic contact layer 50b. The source and drain electrodes 58 and 60 are formed on the ohmic contact layer 50b. A passivation layer 63 is formed on the source and drain electrodes 58 and 60. The pixel electrode 67 is formed on the passivation layer 63 and contacts the drain electrode 60 through the drain contact hole 65.
A black matrix 73 is formed on the second substrate 70 and includes openings. A color filter layer 76 includes the red (R), green (G) and blue (B) color filter patterns 76a, 76b and 76c corresponding to the respective openings of the black matrix 73. A common electrode 79 is formed on the color filter layer 76.
An alignment layer is formed on each of the pixel electrode 67 and the common electrode 79. A liquid crystal layer 90 is formed between the array substrate and the color filter substrate.
In general, the patterned spacer 83 is formed on the color filter substrate attaching the color filter substrate and the array substrate and maintaining a cell gap from each other. The patterned spacer 83 contacts both the color filter substrate and the array substrate. However, when the LCD device 35 is pressed, a restoring force to its original cell gap at the pressed portion is weak resulting in a press defect or a touch defect. This is because an elasticity of the patterned spacer 83 is less than that of the ball spacer made of a silica material. Accordingly, the patterned spacer 83 is not restored as easily due to a friction between the patterned spacer 83 and the array substrate.
To resolve the above mentioned problems, an LCD device including two different types of patterned spacer is developed.
A first patterned spacer of the two patterned spacers contacts both of an array substrate and a color filter substrate in order to function to maintain a cell gap. A second patterned spacer of the two patterned spacer is spaced apart from the first patterned spacer. In a regular state, one end of the second patterned spacer contacts the color filer substrate and the other end of the second patterned spacer does not contact the array substrate. When an external pressure is applied, the other end of the second patterned spacer contacts the array substrate. Accordingly, the second patterned spacer maintains the cell gap along with the first patterned spacer against the external pressure and improves the restoring force, and thus reduces the press defect or the touch defect. In other words, the second patterned spacer functions as a press prevention spacer.
However, when the external pressure is applied and the second patterned spacer contacts the array substrate, the alignment layer of the array substrate may be defected due to the pressure by the second patterned spacer. This causes liquid crystal molecules over the defected portion to be aligned disorderly and operated abnormally resulting in a light leakage.
To resolve the problems, a black matrix corresponding to the second patterned spacer is designed to have a width wide enough to prevent the light leakage around the second patterned spacer. In other words, the width of the black matrix is configured to be 50 μm (micrometers) wider than that of the second patterned spacer. However, an increase of the width of the black matrix causes a decrease of an aperture ratio.
In general, the first and second patterned spacers each have a same cylindrical shape as shown in FIG. 3, and have a diameter of about 18 μm to about 20 μm in consideration of the restoring force and the press prevention. When the diameter of the patterned spacer is about 18 μm, the black matrix is formed to have a width of about 68 μm (18 μm+50 μm).
As described, as the width of the black matrix increases, the aperture ratio decreases, resulting in decreased transmissivity and brightness of displays.